Customize RS ground-plane for GMRS

[conve36]

Anyone know if I could cut down the length of the RS groundplane 20-176 radials for better performance of GMRS freqs? Yes, for transmitting... I know the 1/4 wave of 462.650 is 6.38 inches.... Thanks!

 

[W6KRU]

Cutting the radials will do nothing. The verticals are a different story but I wouldn't do that either. If you need a groundplane for a specific frequency, make your own. It is really easy and a lot cheaper than a sputnik (20-176).

 

[mancow]

Why do you say that? Trimming the short ones a bit should work fine. Plus, by the time he gathers the materials to build a decent reliable rugged one it's probably just as cheap to mod the 176.

 

[conve36]

Why would it cost anything to mod the one I have? I have 3 of them that are just laying around....

 

[W6KRU]

Why do you say that? Trimming the short ones a bit should work fine. Plus, by the time he gathers the materials to build a decent reliable rugged one it's probably just as cheap to mod the 176.

I said that because he asked about trimming the radials. That would only cut down on the groundplane. ??? Reducing the size of the groundplane does nothing until the groundplane becomes inefficient for the freq of interest.

When you say "trimming the short ones a bit", it sounds like you are referring to the vertical elements, not the radials. ???

 

[W6KRU]

Why would it cost anything to mod the one I have? I have 3 of them that are just laying around....

If you have 3 of them just laying around, go for it. But you need to cut the vertical elements, not the radials.

 

[mancow]

Right, I was thinking of the two little shorty Uhf ones. It might actually work as it is. I think they are pretty broad banded.

 

[rvictor]

I think there's agreement that you shouldn't cut the radials.

Why don't you hook it up to an SWR meter just as it is and see what you get. Once you've done that, you will have a better idea of whether any pruning of the vertical elements would be desirable.

Dick

 

[rcvmo]

Trimming the short ones a bit should work fine.

I have three of these mounted across a side arm on my tower, all cut for UHF, 220 MHz, and VHF. Yes much cheaper than spending the time looking for items at a hardware / RS and attempting to construct.
They have weathered well over the last 25+ years. I have the same set-up at my summer cottage only some 70 feet up in a pine tree.
rcvmo

 

[conve36]

Can anyone tell me the exact lengths I should cut the vertical elements and the radials to? For GMRS band, 462.650/467.650.... THANKS!

 

[conve36]

Should I remove the 2 small vertical elements and leave the one that is in the middle cut to a certain length???

 

[SkipSanders]

An alternative, of course, is just to get a nice premade GMRS antenna, which will be MUCH better built, and pre-tuned.

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